1. Field of the Invention
This invention relates to a cellular cordless telephone which can be used in both a cellular system and a cordless system.
2. Description of the Related Art
U.S. Pat. No. 4,989,230 discloses a cellular cordless telephone which operates with both a cordless base station and a cellular base station. One embodiment of the cellular cordless telephone includes a cellular transceiver, a cordless transceiver, an antenna for cellular radio channels, and an antenna for cordless radio channels. Another embodiment of the cellular cordless telephone includes a cellular telephone, a cordless telephone transceiver, an antenna for cellular radio channels, and an antenna for cordless radio channels. Whenever the cellular cordless telephone is within a range of the cordless base station, telephone calls may be made over the cordless radio channel or transferred from the cellular radio channels to the cordless radio channel. If the cellular cordless telephone thereafter moves out of the range of the cordless base station, telephone calls may be made over the cellular radio channels or transferred from the cordless radio channel to one of the cellular telephone channels.
U.S. Pat. No. 4,989,230 indicates that the cordless radio channels are in the frequency band from 46 MHz to 49 MHz while the cellular radio channels are in the frequency band from 824 MHz to 894 MHz.
The cellular cordless telephone of U.S. Pat. No. 4,989,230 has separate radio communication units for a cellular system and a cordless system respectively. Thus, the cellular cordless telephone of U.S. Pat. No. 4,989,230 tends to be large in size and heavy in weight.
In the cellular cordless telephone of U.S. Pat. No. 4,989,230, the two radio communication units consume electric power even when they are in stand-by states. Therefore, the total power consumption rate tends to be high.